Cooling arrangement for hermetically sealed refrigerant compressor



MEAGHER COOLING ARRANGEMENT FOR HERMETICALLY SEALED REFRIGERANTCOMPRESSOR Flled Dec 7, 1959 Apri United States Patent f COOLINGARRANGEMENT FOR HERMETICALLY SEALED REFRIGERANT COMPRESSOR George L.Meagher, Anchorage, Ky., assignor to General Electric Company, acorporation of New York Filed Dec. 7, 1959, Ser. No. 857,948

2 Claims. (Cl. 62-196) The present invention relates to a refrigerantcompressor and is more particularly concerned with a cooling arrangementfor a refrigerant compressor of the type commonly known as a high sidecase in which the pressure within the hermetically sealed compressorcase is approximately the same as the pressure on the high pressure sideof the refrigerating system.

Although the present invention is useful in all types of refrigerationsystems employing a compressor having a high side case, it isparticularly well adapted for use in reversible flow type refrigerationsystems in which the refrigerant flowing through the system can beselectively reversed according to the desires of the operator. Thelatter type of refrigeration system is employed in air conditioningapparatus of the type used for both heating and cooling purposes andsometimes referred to as a heat pump. The refrigeration system of thisapparatus normally includes a pair of heat exchangers one being exposedto air from the outdoors and the other heat exchanger being exposed toair from the enclosure to be conditioned, the two heat exchangers beingconnected by a suitable refrigerant expansion means. A refrigerantreversing valve is used to selectively direct the high pressurerefrigerant gas from the compressor into one or the other of the heatexchangers while directing the suction gas from the opposite heatexchanger into the compressor. Thus, each of the heat exchangers isoperated either as an evaporator or as a condenser according to thedesires of the occupant of the enclosure. During the summer or coolingseason, the inside heat exchanger is generally operated as an evaporatorto cool the air from the enclosure while the outdoor heat exchanger isoperated as a condenser to cool and condense the refrigerant gas flowingfrom the compressor unit. In the winter or heating season, however, therefrigeration system is reversed so that the indoor heat exchangeroperates as a condenser to warm the air passed thereover from theenclosure while the outdoor heat exchanger is operated as an evaporatorto take in heat from the outdoor air being circulated through this heatexchanger.

When using a high side compressor in a refrigeration system, it isnecessary to provide some arrangement for cooling the compressor motorduring the operation of the system. One means for accomplishing thispurpose is to pass the hot discharge gas from the compressor through aprecooling or superheat removal coil and then to direct the precooledgas back into the hermetic case to cool the motor prior to passing thegas into the condenser of the refrigerating sytem. In those systemsusing a superheat removal coil, the coil is normally positioned on thecondenser or outdoor side of the unit and generally forms a portion ofthe outdoor heat exchanger. In a reversible refrigeration system, theabove-described compressor motor cooling arrangement workssatisfactorily in the summer when warm air from the outdoors is passedover the outer heat exchanger that is then operating as a condenser.However, in the winter time, when the indoor heat exchanger is used asthe condenser 2,979,917 Patented Apr. 18, 1961 to supply heat to the airfrom the enclosure, it is not practical to pass the hot discharge gasfrom the compressor into a superheat removal coil located adjacent theoutside heat exchanger so that the heat given up by this gas isdissipated to the outside air. That is, the heat given up by the hotdischarge gas could be more eifectively utilized by the indoor heatexchanger to warm the room air. Also, in the winter time the compressordischarge gas is generally at a much lower temperature so that it mayprovide motor cooling without precooling of the gas. It has been foundthat, in the winter time, the superheat removal coil merely serves tocondense the gas and to cause liquid refrigerant to collect in thecompressor case rather than be discharged therefrom in gaseous form.

It is, therefore, an object of the present invention to provide, for arefrigeration system employing a high side case, an improved dischargegas cooling arrangement that will maintain the motor Within safeoperating temperatures but will not cause liquid refrigerant to collectin the hermetic case when the temperature of the compressor dischargegas is too low.

It is another object of the present invention to provide, for areversible refrigeration system, an improved compressor motor coolingarrangement employing a superheat removal coil associated with theoutdoor heat exchanger structure which will permit efficient operationof the reversible refrigeration system in both directions.

It is a more specific object of the present invention to provide for ahigh side case, a cooling arrangement using a superheat removal coilwhich provides cooling of the motor in accordance with the temperatureexisting in the case.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds and the features ofnovelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

In carrying out the present invention there is provided, in combinationwith a refrigeration system, a compressor and a compressor motorhermetically sealed within a casing. A discharge chamber is providedinto which the compressed refrigerant gas from the compressor isdischarged prior to being directed into a superheat removal coil whereit is partially cooled prior to flowing into the hermetic casing. Thepartially cooled high pressure gas cools the compressor motor beforeflowing out of the case into the remaining portions of the refrigerationsystem. A valve controlled bypass passage leads from the dischargechamber directly into the hermetic casing and provides a means forconducting high pressure discharge gas into the casing directly from thedischarge chamber without passing through the superheat removal coilwhenever there is a predetermined pressure differential between thedischarge chamber and the case. In the superheat removal coil there isprovided a valve means which closes the superheat removal coil inresponse to a temperature responsive device within the case which isenergized whenever the temperature within the case falls below apredetermined temperature thereby blocking the flow of gas through thesuperheat removal coil and forcing it to flow directly through thebypass passage into the case without precooling when the temperaturewithin the case drops below the predetermined temperature.

For a better understanding of the invention reference may be had to theaccompanying drawing, the single figure of which is a schematic view ofa reversible refrigeration system incorporating the present inventionand showing the compressor thereof in cross section.

Now referring to the drawing there is shown a reversible refrigerationsystem including a hermetically sealed compressor 2 having a hermeticcasing 3 in which there is disposed a refrigerant compressor unit 4 anda compressor drive motor 6. The refrigerant compressor unit 4 has anannular compression chamber 7 defined within a defines the upperend-wall of the annular compression chamber, supports the drive shaft12above the eccentric 11 for rotation by the drive motor 6. The mainframe 14 also supports the compressor within the casing. This rotarycompressor is of the type well-known in'the art and contains a blade(not shown) which reciprocates within a slot formed in the compressorcylinder 8 and which wipes against the face of the rotor during itsrotation within the compression chamber thereby dividing the chamberinto high and low pressure sides. The crosssectional drawing of thecompressor shows that portion of the chamber 7 just ahead of the bladewhich is on high pressure side of the compression chamber.

As indicated in the drawing, the compressor unit 2 is in refrigerantflow relationship with a reversing means or valve 16 for reversing thedirection of flow of refrigeantto a pair of heat exchangers 17 and 18.When used in an air conditioning unit, the heat exchangers are arrangedso that one is exposed to outdoor air and the other is exposed to airfrom the enclosure to be conditioned. The reversing valve 16 may be anyof the types of reversing valves well known in the art and maybeelectrically or mechanically operated according to the desires of theoperator of the air conditioner. The reversing valve 16 operates todirect high pressure refrigerant gas into either of the conduits 19 or21 while receiving low pressure gas from the opposite conduit. Duringoperation of the system, low pressure suction gas flows from thereversing valve 16 through the suction line 22 which connects With thesuction port of the compression chamber. The suction port delivers thislow pressure gas into the compression chamber where it is compressedduring rotation of the rotor 9 to a much higher pressure and isdischarged through a discharge port or outlet 23 into a dischargechamber 24. Mounted within the discharge. chamber 24 is a suitable valve26 for assuring proper compression of the gases issuing from thedischarge or outlet port 23 and for preventing the reverse flow of gasback into the compression chamber 7.

In order to cool the high temperature gas prior to passing this gas intothe case there is provided a superheat removal coil 27 having one end 25connecting with the discharge chamber 24 and'the other end 23 leadinginto the case. Most of the coil 27 is arranged outside of the compressorcase 3 and is normally exposed to outdoor air which removes heat fromthe coil. The superheat removal coil 27 is usually included as a part ofthe outdoor heat exchanger structure and is shown adjacent heat exchangecoil 17 which will be considered the outdoor heat exchanger for purposesof explanation. The outlet 28 of the superheat removal coil communicateswith the inside of the casing and discharges the partially cooled gasinto the casing 3 for cooling the motor. After cooling the motor, thehigh pressure gas discharges from the casing through the outlet or highpressure line 29 back to the reversing valve where it is directed intothe remaining portions of the refrigeration system. Gas flowing throughthe superheat removal coil generally remains in gaseous form, but, if asmall amount of refrigerant liquifies in the coil, it is immediatelycarried out of the coil by the gas as it flows into the casing and,under normal operating conditions, the liquid is flashed into gaseousform when carried into contact with the warm motor surfaces.

During operation of the system, as was mentioned be-.

fore; high pressure refrigerant gas is passed either first through theoutdoor heat exchanger 17 'or through the heat exchange 18, which forpurposes of explanation will be considered the indoor heat exchanger,depending upon the particular type of operation desired for the system.

When the unit is operating to cool an enclosure, it will be apparentthat'the outdoor heat exchanger 17 must be utilized as a condenser whilethe indoor heat exchanger 18 acts as an evaporato'r. 'Thus, the exhaustgas is directed from the refrigerant reversing valve 16 first into theheat. exchanger 17, which is exposed to the, outdoor air, where the gasgives up its heat and is condensed into liquid refrigerant. Refrigerantthen flows through a restricting'means, generally designated 31, intothe indoor heat exchanger 18. For purposes to be explained later in thespecification the restricting means is designed to provide greaterrestriction to the flow of refrigerant during the heating cycle thanwhen the system is operated on the cooling cycle. orator pressure as itflows through'the restricting means 31 and upon entering the evaporator,or heat exchanger 18, the refrigerantabsorbs heat from the indoor airbeing circulated over this heat exchanger. The refrigeant vaporizes inthe evaporator and absorbs sufficient heat to raise its temperature verysubstantially. Since the indoor air flowing over the indoor heatexchanger 18, or evaporator, is usually in the 75 F. to 100 F. range,during operation of the system on the cooling cycle, the temperature ofsuction gas is usually raised, for example, to the 60 F. to 70 F. rangeprior to being drawn into the compressor. During the cooling cycle, thisgas is then directed by the reversing valve 16 through the suctionconduit 22 into the compressor where, in the process of compression, thetemperature of the gas increases from 90 to 140 to approximately 160-210F., depending on the original temperature and pressure of the suctiongas. As was pointed out previously the high temperature discharge gas isthen cooled sufiiciently Within the superheat removal coil 27 to providecooling for the compressor motor 6 as it is discharged from'the coil 27into the hermetic casing.

In'the winter or'heating season, the reversing valve 16 is adjusted sothat it directs the hot discharge gas flowing from thedischarge conduit29 into the conduit 21 and thence to the indoor heat exchanger 18. Thisheat exchanger then operates as a condenser and gives up heat to theroom air being passed thereover. The refrigerant is condensed in heatexchanger 18 and is then passed through the restricting means 31 intothe heat exchanger 17 which' is then operated as an evaporator. In theevaporator, or heat exchanger 17, the refrigerant absorbs heat from theoutdoor air being circulated over this heat exchanger and becomesvaporized prior to being directed by the reversing valve 16 back intothe compression chamber. In the winter, or heating cycle operation ofthe system, the suction gas in the evaporator and the in the summertime.

suction conduit 22 leading to the compressor is at a temperatureslightly below that of the air flow over the outdoor heat exchanger 17.Thus, the suction gas in the winter time may be at a temperatureanywhere from 50 on down to or below freezing and is much colder incomparison to the gas flowing through the suction line 22 During thecompression of this suction gas its temperature israised so that itdischarges from the compressor at anyhwere from F. to F. depending onthe original temperature and pressure of the suction gas. This is, ofcourse, much lower than the temperature of the gas discharged during thesummer operation. Obviously, a superheat removal coil of 'suchproportions designed to promote proper cooling of the high temperaturedischarge gas in the summer will be The refrigerant expands toevapcooled to a greater extent by the cold winter air than it would beby the relatively warm summer air. This, of course, creates a furtherdisparity in the amount of cooling received by the gas in the superheatremoval coil during operation on the two different cycles. A furtherdisadvantage in this arrangement is that, during the winter, it isdesirable to remove all of the heat of the discharge gas at thecondenser which would be the heat exchanger 18 during this type ofoperation. Therefore, if the gas is passed through the superheat removalcoil 27, which is exposed to outdoor air, this heat is lost as far asheating purposes are concerned.

It has been found that, under most conditions of operation on theheating cycle, the gas discharged from the compressor is of a low enoughtemperature to cool the motor and requires no further or at least verylittle precooling. In order to pass the discharge gas directly into thecase without passing through the superheat removal coil wheneveradditional cooling is not required, the present invention provides abypass passage 33 leading from the discharge chamber 24 to the inside ofthe casing. A pressure responsive valve means 34 closes the bypasspassage 33 and prevents the flow of refrigerant through the passagedirectly into the casing unless there exists a pressure differentialbetween the discharge chamber 24 and the inside of the casing greaterthan the pressure of the valve 34. In the illustrated embodiment of theinvention the valve means 34 comprises a leaf spring which is seatedacross the outlet side of the bypass passage 33. In order to stop theflow of refrigerant through the superheat removal coil 27, a shut offvalve 36 is provided in the superheat removal coil 27. In theillustrated embodiment of the invention, the shut off valve 36 islocated close to the outlet end 28 of the superheat removal coil forreasons that will be explained later in the specification. The valve 36is operated according to temperature conditions within the case by atemperature responsive means including the temperature sensitive bulb 37located within the case 3 adjacent the motor windings. The bulb 37contains an expansible fluid which operates a fluid motor according totemperatures prevailing within the case and energizes the fluid motor toclose the valve 36 upon sensing a predetermined temperature within thecase, such as the temperature 130 F. The bulb 36 and valve operatingmeans may be any of the well known types now on the market and need notbe explained in greater detail herein except insofar as to state thatthe valve and its sensing means must be capable of closing the superheatremoval coil whenever the temperature within the case falls below apredetermined value, such as the above-mentioned 130 F.

Whenever the temperature within the case falls below this predeterminedtemperature set for operation of the valve 36, for example 130, the bulb37 energizes the valve motor to stop the flow of refrigerant gas throughthe superheat removal coil 27. When this occurs, the pressure build-upwithin the discharge chamber and the superheat removal coil causes thegas to flow directly through the bypass passage 33 into the case. Thisgas is generally at a cold enough temperature to cool the motor and tocarry the heat of the motor directly from the case into the remainingportions of the system, or into the condenser of the system, which willthen be the heat exchanger 18. If, the temperature of the gas beingdischarged is not cold enough to maintain the motor and case temperaturebelow the predetermined temperature, i.e., below 130 F., the valve motor36 then opens the superheat removal coil to permit flow of sufficientrefrigerant therethrough to accommodate the cooling needs of the motor.Thus, during most of the operation of the system on the heating cyclewhen the discharge gas requires no precooling, all of the heat of themotor and all or most of the heat carried by the gas itself is removedfrom the refrigerant at the indoor heat exchanger 18. During the coolingcycle, when the suction gas is .cycle.

at a relatively much higher temperature, and the discharge gasaccordingly needs precooling, the valve 36 remains open to pass the gasthrough the superheat removal coil 27 thereby cooling this gassufficiently to supply the cooling needs of the motor.

It is desirable in the cooling season to maintain the refrigerant in theevaporator for a greater length of time so that it will absorb as muchheat from the outdoor air as possible before flowing into thecompressor. A system which is optimized for operation only on thecooling cycle generally has too little restriction in the refrigerantexpansion means 31 to provide optimum performance when operated tosupply heat. That is, in a system optimized for cooling, the compressornormally circulates refrigerant through the evaporator faster than thesurface can evaporate the refrigerant when the system is operated on theheating cycle. The compressor then pumps unevaporated refrigerant andthe system efliciency is low. In order to overcome this problem, thesystem of the present invention incorporates a variable restriction forthe gas expansion means. Thus, during the summer or cooling operation, avalve 39 is actuated to permit refrigerant flow only through therelatively short capillary 31a. However, during the winter or heatingseason, the valve 39 is actuated to permit refrigerant flow only throughthe relatively long capillary 31b to increase the restriction betweenthe heat exchangers during the heating season. The increased restrictioncauses subcooled liquid refrigerant to build up in the indoor heatexchanger 18 to a much greater extent than during operation with therelatively short capillary 31a. This, in turn, increases the condensingtemperature and pressure of the indoor heat exchanger 18 and therebyreduces the pumping rate of the compressor to a level required tocirculate only enough refrigerant through the outdoor heat exchanger 17that can be fully evaporated by the outdoor air flowing over this heatexchanger. This creates a more efficient refrigeration system because iteffectively prevents the pumping of unevaporated refrigerant from theevaporator, or heat exchanger 17, through the compressor. The valve 39may be'operated in any well known manner, however, it is contemplatedthat it be actuated to its cooling or heating positions at the same timeas the reversing valve 16 is moved to change the direction ofrefrigerant flow through the heat exchangers.

Operation of the system with the greater restriction 31b between theheat exchangers would normally create an overcharged condition in thesystem as well as an unreasonably high head pressure. However, in thearrangement of the present invention, with the valve 36 preventingrefrigerant from flowing through the desuperheater coil into the case,there is provided a convenient means for removing some of therefrigerant from the system during the heating season. That is, sincethe inlet end 25 of the superheat removal coil 27 is exposed to the highpressure gas, the coil 27 operates as a trap and causes some of therefrigerant of the system to condense out and collect Within the coilthereby effectively removing it from the system. This reduces the headpressure as well as adjusting the effective refrigerant charge withinthe system for optimum performance during the heating It has been foundthat a 10-foot coil of inch tubing having an .017 inch wall thicknesswill hold approximately /2 pound of condensed Freon 22 at 40 F! Thus, inthe illustrated refrigeration system, when the restriction is increasedas the unit is changed from the cooling to the heating operation, therefrigerant is permitted to condense out of the system and to collect inthe superheat removal coil so that the head pressure is not quite sogreat and the flow through the system is much slower thereby permittingcomplete evaporation of the refrigerant in the evaporator. This featureadapts the refrigeration system to provide a more eflicient type ofrefrigerant flow for the temperature conditions that usualy P l d ringthe heating season.

cooled under all suction gas temperature conditions by using a superheatremoval coil that is controlled by the temperature within the case.Moreover the present-1nvention makes it possible to utilize a compressormotor cooling arrangement, including a superheat removal coil associatedwith theoutdoor heat exchanger structure, in a reversible refrigerationsystem while obtaining reasonably eflicient operation of therefrigeration system for both cooling and heating purposes.

While in accordance with the patent statutes there has been describedwhat at present is considered to be the preferred embodiment of theinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made therein without-departing from theinvention and it is, therefore, the intent of the appended claims tocover all such changes and modifications as fall within the true spiritand scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a reversible refrigeration system, the combination comprising ahermetically sealed casing for containing a high'pressure refrigerantgas, a compressor and a compressor motor 'mounted'in said casing, areversing valve, a suction line for delivering low pressure refrigerantgas from said reversing valve to said compressor, ahigh pressure linefor delivering high pressure refrigerant gas from said casing to saidreversing valve, a discharge chamber directly connected to the outlet ofsaid compressor, a

superheat removal coil having its inlet communicating with saiddischarge chamber and its outlet connecting with said casing thereby tocool the high pressure refrigerant gas from said compressor and todischarge said partially", cooled gas into said casing to cool saidcompressor motor,

a bypass passage connecting saiddischarge chamber directly with saidcase, valve means in said bypass passage for admitting refrigerant fromsaid dischargechamber into said case upon a predetermined pressuredifferential between said discharge chamber and said case, valve meansin said superheat removal coil for closing said superheat removal coil,and means in said case responsive to the temperature within said casefor actuating said valve means to close said superheat removal coil whensaid temperature within said case falls below a predeterminedtemperature thereby to cause discharge gas to flow directly through saidbypass passage into said case without precooling when 'said't'emperaturewithin said case drops below said' predetermined temperature. V 1 2. Ina reversible refrigerating system, the combrnatwn comprising ahermetically sealed casing for containing a high pressure refrigerantgas, a compressor and a comp'ressor motor mounted in said casing, areversing valve, a

suction line for delivering low pressure refrigerant gas from saidreversing valve to said compressor, a'high pres sure line for deliveringhigh pressure refrigerant gas from said casing to said reversing valve,a pair of heat ex changers connected in refrigerant flow relationshipwith saidreversing valve and having connected therebetween a flowrestricting means, means in said system for interjecting greater flowrestriction betweensaid heat ex-1 changers whe'nfiow of refrigerant isin one directio'n than' when the flow of refrigerant is in theotherdirection; a discharge chamber directly connected to the outlet'of saidcompressor, a superheat removal coil'havingits inlet communicating withsaid discharge chamberarid said outlet connecting with saidcasingthereby to cool the high pressure refrigerant gas from said compressorand to discharge said partially cooled gas into said casing to cool saidcompressor motor, a bypass passage connecting said discharge chamberdirectly with said case, valve means in said bypass passage foradmitting refrigerant from said discharge chamber into said casing upona predetermined pressure differential between said discharge chamber andsaid case, valve means in said superheat removal coil adjacent theoutlet end of said superheat removal coil for closing said superheatremoval coil, and means in said case responsive to the temperaturewithin the case for actuating said valve means to close said superheatremoval coil when the temperature within said ease falls below apredetermined temperature so that discharge gas is forced to flowdirectly through said bypass'passage into said case without precoolingand whereby some refrigerant is condensed into liquid form in saidsuperheat removal coil and stored therein whensaid temperature of saidcase drops below said predetermined temperature.

References Cited in the fileof this patent UNITED STATES PATENTS2,482,569 Zearfoss Sept. 20, 1949 2,720,756. Stebbins Oct. 18, 19552,746,266 Kosfield May 22, 1956 2,904,971 KOSfiGld Sept. 22, 1959

